Trucks are typically backed into or in close proximity to a loading dock or other opening in a building wall to facilitate loading and unloading of the truck. Since the width of the dock opening is typically larger than the truck width so that vehicles of different sizes can be readily serviced, a gap is formed between the loading dock walls and the truck which exposes the interior of the building to the outside weather and permits rain and cold air to enter the dock opening and the building. Attempts to seal the interior of the building from the outside environment have included loading dock shelters which utilize fabric or sheet material to form walls or curtains between the opening and the truck and loading dock seals which utilize resilient, compressible pad members, generally disposed at the lateral and top edges of the opening, to sealably engage the walls or rear edges of the truck. Some of the typical loading dock seals have square, beveled, wedge-shaped or L-shaped seals on the side.
In both loading dock seals and shelters, it has been common to use a head curtain supported by a header frame assembly to seal the gap between the truck roof and the top of the loading dock door so as to accommodate different truck sizes, door sizes, or truck orientations relative to the loading dock where seals may not be practical. In such applications, a common problem is the rain water which infiltrates between the head curtain and the top of the truck, into the rear truck opening, the loading dock, or the building. Such infiltration of water may cause serious problems including unsafe and slippery operating conditions, damage to materials being loaded and unloaded into the truck and damage to the building and loading dock facilities. The rain water typically originates from the water runoff down the side of the building and the header assembly of the loading dock. The rain runoff is also collected on the roof of the truck and is aggravated by sloped driveways found in many loading docks.